Genomic repertoire of human mesangial cells: comprehensive analysis of gene expression by cDNA array hybridization

Knowing when and where a gene is expressed in a cell often provides a strong clue as to its physiological role. It is estimated the human genome contains 80 000-100 000 genes. Assessment of gene activity on a global genome-wide scale is a fundamental and newly developed experimental strategy to expand the scope of biological investigation from a single gene to studying all genes at once in a systematic way. Capitalizing on the recently developed methodology of cDNA array hybridization, we monitored the simultaneous expression of thousands of genes in primary human mesangial cells. Complex alpha-P-33-labelled cDNA probes were prepared from cultured mesangial cells. The probe was hybridized to a high-density array of 18 326 paired target genes. The radioactive hybridization signals were analysed by phosphorimager. Bioinformatics from public genomic databases was utilized to assign a chromosomal location of each expressed transcript. Approximately 7460 different gene transcripts were detected in mesangial cells. Close to 13% (957 genes) were full-length mRNA human transcripts (HTs), the remainder 6503 being expressed sequence tags (ESTs). Using special imaging computer software, the transcriptional level of the 957 HTs was compared with the expression of the ribosomal protein S28 (housekeeping gene). The HTs were also classified by function of the gene product and listed with information on their chromosomal loci. To allow comparison between clinical and experimental studies of gene expression, the detected human gene transcripts were cross-referenced to orthologous mouse genes. Thus, the presented data constitute a quantitative preliminary blueprint of the transcriptional map of the human mesangial cell. The information may serve as a resource for speeding up the discovery of genes underlying human glomerular diseases. The complete listing of the full-length expressed genes is available upon request via E-mail: (Abdalla_Rifai@Brown.edu).